There is currently a demand for apparatus which provides viewers with the illusion of 3D images which appear to exist and interact alongside real objects and people, or ‘float’ in open space. This is especially useful in concert performances and presentations, where impressive visual effects can enhance the viewing experience.
Apparatus are known which create illusions of 3D images interacting with real objects. For example EP0799436A1 describes an apparatus for representing moving images in the background of a stage or the like using an image source. The article to be represented is projected by the image source (projector) on to a reflecting surface parallel with the stage, and then undergoes secondary reflection in a transparent smooth foil angled at 45° to the audience in such a way that the image appears to the viewer on the background of the stage. The image observed is a flat two-dimensional (2D) image which simply produces the illusion of being 3D. This is an embodiment of the well-known “Pepper's Ghost” illusion. The viewing experience is deteriorated when, for example, the stage is viewed from an acute angle and the image no longer appears to represent its intended 3D form. Such apparatus is also expensive and difficult to implement because it requires a number of reflecting surfaces, high intensity and high definition projection means and high tension of the reflecting foil to ensure stable images.
Stereoscopy is a well-known effect used in cinema to produce the illusion of 3D images. Each eye of the viewer is presented with the same scene depicted from slightly different perspectives. One way to achieve this effect is to use a polarised 3D system, wherein light-polarising filters are used to produce two images of different polarisation. Filters worn by the viewer over each eye then allow the right eye to see one image and the left eye to see another, creating the stereoscopic 3D effect. In order for the effect to be convincing, the image intended for the left eye should be effectively ‘blocked’ by the right-eye filter, and vice-versa. If this is not achieved completely then the undesirable effect of ‘ghosting’ may be observed and the illusion is not complete. In polarised 3D systems, ghosting is avoided by ensuring that the polarisation of the reflected light is retained so that it may be effectively blocked by the viewer's eye filters.
Existing 3D projection screens use screens which are painted with a metal-containing paint so that reflected light retains its original polarisation. This avoids ghosting and the illusory effect is more impressive than regular 2D projection, but the viewer is aware that they are watching a projected image and the illusory effect is thereby limited.
The present invention provides a projection screen, projection apparatus and projection method. These provide the viewer with an enhanced viewing experience, creating the illusion of images, in particular 3D images, which may exist alongside and interact with real objects. The present invention provides apparatus which is lightweight, low-cost and easy to transport and install. The use of a stereoscopic projection system to represent 3D images provides an enhanced visual effect by providing the viewer with binocular depth cues rather than the more inferior monocular depth cues provided by existing apparatus such as disclosed in EP0799436A1. Furthermore, the particular projection screen used may provide the illusion that the 3D images are ‘floating’, in other words existing alongside real objects, creating an impressive visual experience for the viewer.